1. Field of the Invention
This invention relates to electronic musical instruments, such as organs, and more specifically, to a key switch assembly for use therein.
2. Description of the Background Art
In U.S. Pat. No. 3,342,967 of John R. Brand et al, a switch construction for use in an electronic musical instrument, such as an organ, is shown to include a switch body having divergent and self-biasing leaf spring members terminating in their free ends in a bifurcated contact. The contacts ride on the surface of a printed circuit board between selected conductive areas so as to cause a connection to be made between the bifurcated contacts. The leaf spring is caused to be resilient so as to avoid the necessity for additional biasing means in the device. The switch is arranged to develop a feel to the fingertip of the operator indicative of the switch position and the contact action.
Stanley Cutler, in U.S. Pat. No. 3,657,460, shows a keyboard switching assembly having a row of resilient switch members connected to a loudspeaker apparatus and positioned to be individually deflected upwardly against the contact assembly. The contact assembly includes a circuit board having conductive pads above the switch members. The switch members are actuated by the depression of a key to cause the upward deflection of the switch member against a portion of a conductive elastic strip normally spaced from an associated conductive pad.
In U.S. Pat. No. 3,769,869, Carl S. Nelson, Jr. discloses an electronic instrument switch which includes a cylindrical wire connected to a tone generator and a strip of conductive elastic material deflectible against the wire to have variable contact therewith. A lubricant is provided to permit the elastic material to spread smoothly outwardly under the pressure. An insulator strip is secured to the elastic conductive strip and a second elastic conductive strip is fastened to the insulator strip and grounded to shield the first conductive strip.
William S. Scheingold et al, in U.S. Pat. No. 3,909,564, show a keyboard assembly wherein a key acts on a spring member provided with a sliding portion movable to cause closing of contacts deposited on a flat flexible cable.
Masakatu Iijima shows, in U.S. Pat. No. 4,186,638, a keyboard device wherein a printed circuit board is provided with pairs of stationary contacts and a common movable contact made of rubber for connecting each pair of stationary contacts. The movable contact member is placed on the printed substrate and holding members provided on a keyboard frame restrict lateral expansion thereof when the movable contact member is brought into contact with the stationary contacts by depression of the keyboard keys.
The switching devices of the cited art present a number of problems such as the requirement of maintaining high accuracy and low tolerances in the assembly. This requirement results in relatively high cost of the assembly. Another problem in the use of such switching devices in keyboard electrical instruments was in the variation in the key resistance to movement as the key is depressed from the undepressed to the fully depressed position in playing the musical instrument. It is highly desirable in such instruments to provide for a key depression with minimum variation in the force required to depress the key over the range of movement from the undepressed to the fully depressed condition. It is further desirable to prevent discontinuities in the resistance force over the range of movement of the key.